Prosthesis for annuloplasty comprising a perforated element

ABSTRACT

A prosthesis for annuloplasty comprising a laminar or tubular element having a plurality of apertures along at least one portion. Preferably, the shape, dimensions, and arrangements of the apertures in this prosthesis are chosen in such a way as to give the prosthesis a differentiated flexibility in dependence on the location and direction of application of an external stress.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 10/393,448, entitled “PROSTHESIS FOR ANNULOPLASTY COMPRISING APERFORATED ELEMENT” filed Mar. 20, 2003 by Pietro Arru et al., whichclaims the benefit of European Patent Application No. 02425190.2 filedMar. 27, 2002. Each of the foregoing U.S. and European patentapplications is incorporated herein by reference in its entirety. Anydisclaimer of claim scope that may have occurred during the prosecutionof the above-referenced application(s) is hereby expressly rescinded.

TECHNICAL FIELD

The present invention relates in general to a device for cardiac valverepair operations and, in particular, to a prosthesis for annuloplasty.

BACKGROUND

The human heart has four cardiac valves: the mitral valve, the tricuspidvalve, the pulmonary valve and the aortic valve. The mitral valve issituated in the left atrio-ventricular ostium and regulates theunidirectionally of the flow of blood from the atrium to the ventricle.It opens in the diastole and closes in the systole, preventing bloodfrom flowing back from the ventricle to the atrium. The annulus of anormally functioning mitral valve is characterized by shape, dimensionsand flexibility such as to allow a correct closure of the valve lipsduring the systolic phase. For example, the mitral annulus has acharacteristic “kidney” shape (of “D” shape), and is more flexible inthe portion corresponding to the posteria lip of the valve. Illnesses orgenetic defects can cause deformations or dilatations of the annulus ofthe mitral valve, resulting in an incomplete closure thereof withconsequent regurgitation of blood. The same phenomena can occur in thetricuspid valve, situated between the right atrium and right ventricle.

A frequently used method for eliminating some pathological alterationsof the mitral and tricuspid valves is that of reinstating the correctshape and dimensions of the valve annulus by means of surgicalprocedures known as annuloplasty. Annuloplasty comprises surgicallyimplanting a supporting prosthesis on the dilated or deformed annulusfor the purpose of reinstating its dimensions and/or physiological shapein such a way as to allow the cardiac valve to function correctly.

Support prostheses utilized in valve repair operations are calledannuloplasty prostheses. In the majority of cases such prostheses areconstituted by a closed or open ring structure comprising an inner coreand an outer cladding of biocompatible material which allows surgicalsuture.

Annuloplasty prostheses of various types have been described in theprior art. Initially, the prostheses proposed were predominantly of therigid type for the purpose of drastically reducing the dilatation of thevalve annulus. Such prostheses are generally constituted by a metal core(for example, a titanium alloy), an optional sheath of cladding aroundthe core, and an outer cladding of textile for suturing. Rigidannuloplasty prostheses are described, for example, in U.S. Pat. No.4,055,861 by Carpentier et al., issued Nov. 1, 1977, and U.S. Pat. No.3,656,185 by Carpentier et al., issued Apr. 18, 1972.

Rigid prostheses, although satisfactory as far as reinstatement of theshape and dimensions of the valve annulus are concerned, do not allowthe annulus of the valve to flex along the base of the posterior cuspidin such a way as to assist the cardiac muscle movements. Consequently,significant stress is imposed on the suture points subjected to torsionand traction, which prevents natural behavior of the valve.

Subsequently, semi-rigid or completely flexible prosthesis models wereproposed. Completely flexible annuloplasty prostheses are described, forexample, in U.S. Pat. No. 5,041,130 by Carpentier et al., issued Aug.20, 1991, U.S. Pat. No. 5,716,397 by Myers et al. issued Feb. 10, 1998,U.S. Pat. No. 6,102,945 by Campbell et al., issued Aug. 15, 2000, andU.S. Pat. No. 5,064,431 by Gilbertson et al., issued Nov. 12, 1991. Thecompletely flexible prostheses follow the movements of the annulusduring the cardiac cycle in an optimal manner. However, they have thedisadvantage of not allowing the shape to be reconstructed in an optimalmanner.

Semi-rigid prostheses seek to unite the advantages of the rigid typewith those of the completely flexible type while avoiding thedisadvantages of each. Semi-rigid annuloplasty prostheses are described,for example, in U.S. Pat. No. 5,061,277 by Carpentier et al., issuedOct. 29, 1991, U.S. Pat. No. 5,104,407 by Lam et al., issued Apr. 14,1992, U.S. Pat. No. 5,674,279 by Wright et al., issued Oct. 7, 1997,U.S. Pat. No. 5,824,066 by Gross et al., issued Oct. 20, 1998, U.S. Pat.No. 5,607,471 by Seguin et al., issued Mar. 4, 1997, and U.S. Pat. No.6,143,024 by Campbell et al., issued Nov. 7, 2000.

In particular, U.S. Pat. No. 5,104,407 describes a ring prosthesiscomprising an annular support element which is substantially more rigidin one part than in the remainder. This more rigid part projectstransversely with respect to the general plane in which the remainingpart of the support element lies. On the other hand, U.S. Pat. No.5,607,471 describes a ring prosthesis having variable transversesections, and therefore differentiated rigidity along itscircumferential extent.

All these known prostheses have, however, limitations in relation to thepossibility of exhibiting a variable rigidity in dependence on the pointand/or mode of application of the stresses. For example, U.S. Pat. No.5,104,407 provides a structure with variable rigidity in the plane ofthe ring, but with a limited possibility of flexure outside this plane.On the other hand, U.S. Pat. No. 5,607,471 describes technicalarrangements able to guarantee an improved flexibility out of the planeof the annulus. However, the possibility of effectively obtainingcharacteristics of variable rigidity of the prosthesis, for example, inits localised portions as well, appears significantly limited by thenecessity to vary the area of the entire resistant section of theinternal element. Moreover, the technical arrangements described in U.S.Pat. No. 5,607,471 do not allow an optimal behavior of the prosthesis inresponse to stresses in a tangential direction to be obtained (that isto say stresses directed along its longitudinal axis, which is usuallyclosed in a ring), the rigidity in response to traction and compressionat the same point of the internal element being substantiallyundifferentiated.

SUMMARY

The present invention provides a prosthesis for annuloplasty, therigidity of which can be made variable in a described manner independence on the point, direction and mode (traction, compression,flexion, torsion) of application of the stresses. According to theinvention, this is achieved thanks to a prosthesis for annuloplastycomprising a laminar or tubular element having a plurality of aperturesin at least one portion. This element can then be defined hereinafter inthe present description as “perforated.” In the perforated element, theapertures can be formed substantially according to any arrangement andwith any shape and dimensions, so as to obtain the desired rigidityvariation. For example, a prosthesis provided with such a perforatedelement can have markedly different rigidity whilst having a constanttransverse section, so as to satisfy possible requirements of uniformityof dimensions.

The perforated element can be formed in its laminar form both with aflat development and with various three-dimensional shapes. Preferably,however, the perforated element is made in a tubular shape because thisshape allows a more flexible and efficient arrangement of the aperturesfor the purpose of influencing the properties of rigidity of prosthesis.As a matter of fact, the transverse section of the perforated tubularelement can be of any shape. A circular transverse section is preferredfor reasons of practicality and simplicity of production.

The prostheses of the invention have the additional advantage of aneasier suturability since the apertures formed in the perforated elementcan constitute, if necessary, preferential transit ways for the passageof a suture needle.

There are no particular limitations in relation to the material usablefor the production of the perforated element. The perforated element canbe produced in metal, polymeric, or composite material. For their part,the apertures can be formed in the perforated element with anyconventional technology. For example, if the perforated element is madeof metal, the apertures can be formed by piercing a pre-formed tube by alaser, electroerosion, or cutting. If the perforated element were formedof polymeric material, it could be directly formed into its definitiveshape by moulding technologies. Overall, therefore, the production ofthe prosthesis of the invention is simple and economical.

Further advantages and characteristics of the invention will becomeapparent from the following detailed description provided purely by wayof non-limitative example, with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view, partially in section, of a prosthesis of theinvention of closed ring type (or “closed loop type”).

FIG. 2 is a prospective view, on an enlarged scale, of a tubular elementforming part of the prosthesis of FIG. 1.

FIGS. 3 to 6 are perspective views of respective alternative embodimentsof the tubular element of FIG. 2.

FIG. 7 is a plan view, partially in section, of a further alternativeopen ring type (or “open loop type”) embodiment of the prosthesis of theinvention.

DETAILED DESCRIPTION

The reference 10 indicates in FIG. 1 a prosthesis for annuloplasty. Theshape of this prosthesis generally reproduces the geometry of theannulus of a mitral valve. This prosthesis has a closed ring shaped inthe form of a D with an approximately rectilinear intertrigonal section12 and a curved section 14. The prosthesis 10 is externally clad, in amanner known per se by a sheath 16 of biocompatible material. Preferablythe sheath is made from materials chosen from the group consisting ofpolymers, synthetic textiles, biological tissues and their combinations.The sheath 16 covers a tubular ring element 18 having a transversesection of constant circular shape over its entire extent. The element18 has in its wall (FIG. 2) a plurality of circular apertures 20 spacedalong two lines parallel to the longitudinal axis 22 of the element 18and diametrically opposite one another across the axis 22 in such a waythat the apertures 20 have a spatial orientation substantially parallelto the general plane of the prosthesis 10. Preferably, there are no suchapertures in the intertrigonal section 12, which must be more rigid,whilst they gradually become more closely spaced towards the centralpart of the curved section 14, which must be more flexible. The internalcavity of the element 18 may possibly be filled, partially or totally,with elastomeric material 23, in particular silicone, polyurethane andtheir mixtures, as for example described in U.S. Pat. No. 10/164,358,filed Jun. 5, 2002, the contents of which are hereby incorporated hereinby reference.

The surface of the tubular element 18 and/or of the sheath 16 can beclad partially or totally with a thin layer of hemocompatible carbon,for example turbostratic carbon. The procedure for the production ofsuch a cladding is, for example, described in U.S. Pat. Nos. 5,084,151,5,387,247, 5,370,684, 5,133,845 and 5,423,886, the contents of each ofwhich are hereby incorporated herein by reference. This claddingcontributes to an improved hemocompatibility of the prosthesis 10 and toa controlled tissue growth of the receiving organism.

FIG. 3 illustrates an alternative embodiment of the tubular element 18,which has, in addition to the apertures illustrated in the precedingFIG., further apertures 20 disposed along two lines parallel to thelongitudinal axis 22 of the element 18 and diametrically opposite acrossthe axis 18 so as to have a substantially transverse spatial orientationwith respect to the general plane of the prosthesis 10. The presence ofapertures 20 in the arrangement just described influences the rigiditycharacteristics of the prosthesis 10 under the action of stresses whichact both in the general plane and transversely with respect to it. Inparticular, the prosthesis can be rendered, for example, less rigidagainst stresses which act in its general plane along anantero-posterior direction (that is to say in a direction distinguishedby the reference numeral 24 in FIG. 1), with respect to stresses whichact in the general plane along a direction orthogonal to theantero-posterior direction. As far as the rigidity characteristicsagainst stresses which act transversely with respect to the generalplane of the prostheses 10 are concerned, they are for example chosen insuch a way as to facilitate the assumption of a saddle shape in certainphases of the cardiac cycle.

The desired characteristics of variation in flexibility can also beobtained with a suitable variation of the dimensions of the apertures 20of the element 18, as illustrated for example in FIG. 4.

FIG. 5 illustrates a further embodiment of the tubular element 18, inwhich the apertures 20 are formed in the shape of rings interruptedalong a generatrix by a bridge 26 connecting adjacent portions 28, alsoof annular shape, of the tubular element 18. Such apertures 20 can becharacterized by their extent (a) in the axial direction, the extent (b)in the axial direction of the tubular portions 28 interposed between twoadjacent apertures 20, and the extent (c) of the bridges 26 in thecircumferential direction. The values of (a), (b), and (c) can beselected independently at will and maintained constant or made to varyalong the axial extent of the element 18 so as to determine the rigidityof the prosthesis 10 in a desired manner in dependence on the point anddirection of application of the stresses.

FIG. 6 illustrates a further embodiment of the tubular element 18, inwhich the apertures 20 have a sinuous shape limited in one or moreportions by edges 30 in contact, or almost in contact, in the absence ofexternal stresses. A prosthesis provided with a perforated tubularelement 18 of this type opposes enlargement of the apertures 20 with apredetermined force in response to a traction stress, allowing theprosthesis to extend in the axial direction, whilst further closure ofthe apertures 20 in response to a compression stress is in factprevented by the contacting edges 30, so that the behavior of theprosthesis is similar in this case to that of a rigid body. Such aprosthesis thus has differentiated rigidity in response to stressesacting in the axial direction, being rather rigid in response tocompression stresses but on the other hand deformable in response totraction stresses acting in the opposite sense along the same direction.Such behavior is particularly convenient for encouraging, on the onehand, the natural dilatation of the annulus in the diastolic phase and,on the other hand, to guarantee the absence of compression andcorrugation phenomena (pleating) following surgical suture during avalve repair operation.

It goes without saying that the arrangements of the apertures 20previously illustrated and/or described can be combined in any way indifferent portions of the same perforated element 18 so as to regulatethe rigidity of the prosthesis 10 in a desired manner in dependence onthe point and direction of application of the stresses. Equally it isalso possible, in embodiments of the perforated element 18 notillustrated, to arrange the apertures in an irregular manner rather thanin a regularly repeating pattern.

FIG. 7 illustrates a further embodiment of the prosthesis of theinvention having an open ring shape and having a perforated element 18of laminar or tubular structure. In this case, too, by varying theshape, dimensions and/or spacing of the apertures 20 it is possible toobtain the desired variations in rigidity.

Naturally, the principle of the invention remaining the same, thedetails of construction and the embodiments can be widely varied withrespect to what has been described purely by way of example, without bythis departing from its ambit.

1. An annuloplasty prosthesis for repair of a cardiac valve annulus byaffecting the dimensions or shape of the valve annulus, so as to improveperformance of the cardiac valve, the prosthesis comprising: a ringelement having a longitudinal axis, a curved portion, and a generallystraight portion, the ring element configured to have a shape generallycorresponding to a desired shape of a normal cardiac valve annulus; anda sheath covering at least a portion of the ring element; wherein thering element defines a plurality of apertures each having acharacteristic selected to effect the flexibility of the annuloplastyprosthesis.
 2. The annuloplasty prosthesis of claim 1 wherein thecharacteristic includes one or more of a size, a shape, and a locationalong the longitudinal axis.
 3. The annuloplasty prosthesis of claim 1wherein the apertures are configured such that the curved portion ismore flexible than at least the straight portion.
 4. The annuloplastyprosthesis of claim 1 wherein the ring element is an open ring having afirst end and a second end.
 5. The annuloplasty prosthesis of claim 1wherein the ring element has a tubular cross-section.
 6. Theannuloplasty prosthesis of claim 1 wherein the ring element has alaminar cross-section.
 7. An annuloplasty prosthesis comprising a ringelement having a size and a shape generally corresponding to a cardiacvalve annulus, the ring element including a plurality of apertures forcontrolling the flexibility of the annuloplasty prosthesis.
 8. Theannuloplasty prosthesis of claim 7 wherein the apertures are disposedalong at least a portion of the ring element and are configured suchthat the prosthesis has a desired non-uniform flexibility along itslength.
 9. The annuloplasty prosthesis of claim 7 wherein the aperturesare configured such that the prosthesis has a differentiated flexibilitydepending on the location and direction of application of an externalstress.
 10. The annuloplasty prosthesis of claim 7 wherein theprosthesis is generally planar, and wherein the apertures are configuredsuch that the prosthesis has a first flexibility in response to a firstexternal stress acting in the general plane of the prosthesis and asecond flexibility in response to a second external stress actinggenerally transverse to the general plane of the prosthesis.
 11. Theannuloplasty prosthesis of claim 7 wherein: the ring element has a firstportion and a second portion; and at least one of a size, a shape, or aposition of each aperture is selected such that the first portion ismore flexible than at least a part of the second portion.
 12. Theannuloplasty prosthesis of claim 7 wherein the ring element has a curvedportion and a straight portion, and wherein the apertures are configuredsuch that the curved portion is more flexible than the straight portion.13. The annuloplasty prosthesis of claim 12 wherein the curved portionincludes first and second end regions and a center region therebetween,and wherein the apertures are configured such that the center region ismore flexible than the first and second end regions.
 14. Theannuloplasty prosthesis of claim 7 wherein the ring element is an openring having first and second ends.
 15. A method of forming anannuloplasy prosthesis, the method comprising: forming a plurality ofapertures in a laminar or tubular element, including configuring theapertures such that the laminar or tubular element has a desirednon-uniform flexibility along its length; and forming the laminar ortubular element into a ring element having a shape generallycorresponding to a shape of a natural cardiac valve annulus.
 16. Themethod of claim 15 wherein forming the plurality of apertures includesselecting at least one of a size, a shape, and a location of eachaperture such that the laminar or tubular element has a desirednon-uniform flexibility along its length.
 17. The method of claim 15wherein forming the plurality of apertures includes configuring theapertures such that the prosthesis has a differentiated flexibilitydepending on the location and direction of application of an externalstress.
 18. The method of claim 15 wherein: forming the laminar ortubular element into a ring element includes forming a generally planarring element; and forming the plurality of apertures includesconfiguring the apertures such that the annuloplasty prosthesis has afirst flexibility in response to a first external stress acting in thegeneral plane of the ring element and a second flexibility in responseto a second external stress acting generally transverse to the generalplane of the ring element.
 19. The method of claim 15 wherein: formingthe laminar or tubular element includes forming the laminar or tubularelement into a ring element having a curved portion and a generallystraight portion; and forming the plurality of apertures includesconfiguring the apertures such that the curved portion is more flexiblethan at least a part of the straight portion.
 20. The method of claim 15wherein forming the laminar or tubular element includes forming thelaminar or tubular element into an open ring element having a centerportion and first and second ends.